Project Summary Erythropoiesis is a highly regulated process that generates a large number of red blood cells from hematopoietic progenitor cells. During this process tissue-restricted transcription factors like GATA1 operate together with ubiquitous transcription factors to turn on erythroid transcription programs and silence non- erythroid genes. Transcription factor TFII-I is a ubiquitously expressed transcription factor that has previously been shown to regulate erythroid-specific genes. Recent genome-wide studies demonstrated that TFII-I associates with erythroid-specific genes, with genes encoding cell cycle regulators, and with stress-response genes. The proteomic analysis revealed that TFII-I interacts with chromatin remodeling complexes, with topoisomerases, with components of the cohesin complex, with transcription elongation factors, and with E2F transcription factors. We propose to study the function of TFII-I during erythropoiesis using conditional erythroid-specific ablation of TFII-I function in mice, biotinylation tagging of TFII-I in HUDEP2 cells followed by determination of TFII-I interacting proteins and associated sites in the genome, and mechanistic studies analyzing the functional relationship between TFII-I and E2Fs, as well as between TFII-I and transcription elongation factors during proliferation of erythroid cells and in response to cellular stress. The results from these studies are expected to uncover fundamental new aspects of TFII-I function which may benefit future strategies to combat red blood cell disorders.